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Day 1

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Shadowfacts 2018-12-01 13:51:14 -05:00
parent 5944dd6ce8
commit 3db1e578f0
Signed by: shadowfacts
GPG Key ID: 94A5AB95422746E5
3 changed files with 1014 additions and 0 deletions
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37
lib/day1/day1.ex Normal file
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defmodule Day1 do
def calculate_frequency(shifts) do
shifts
|> Enum.reduce(0, &+/2)
end
def first_repetition(shifts, index \\ 0, sum \\ 0, seen \\ [0]) do
sum = sum + Enum.at(shifts, index)
next_index = rem(index + 1, Enum.count(shifts))
cond do
Enum.member?(seen, sum) ->
sum
true ->
first_repetition(shifts, next_index, sum, [sum | seen])
end
end
def parse_input() do
File.read!("lib/day1/input.txt")
|> String.split("\n")
|> Enum.map(fn s ->
{num, _} = Integer.parse(s)
num
end)
end
def part1() do
parse_input()
|> calculate_frequency()
end
def part2() do
parse_input()
|> first_repetition()
end
end

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lib/day1/input.txt Normal file
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test/day1_test.exs Normal file
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defmodule Day1Test do
use ExUnit.Case
doctest Day1
test "calculate frequency" do
assert Day1.calculate_frequency([1, -2, 3, 1]) == 3
assert Day1.calculate_frequency([1, 1, 1]) == 3
assert Day1.calculate_frequency([1, 1, -2]) == 0
assert Day1.calculate_frequency([-1, -2, -3]) == -6
end
test "first repetition" do
assert Day1.first_repetition([1, -2, 3, 1]) == 2
assert Day1.first_repetition([1, -1]) == 0
assert Day1.first_repetition([3, 3, 4, -2, -4]) == 10
assert Day1.first_repetition([-6, 3, 8, 5, -6]) == 5
assert Day1.first_repetition([7, 7, -2, -7, -4]) == 14
end
end